Posts tagged EEG
Posts tagged EEG
The brain has been traditionally viewed as a deterministic machine where certain inputs give rise to certain outputs. However, there is a growing body of work that suggests this is not the case. The high importance of initial inputs suggests that the brain may be working in the realms of chaos, with small changes in initial inputs leading to the production of strange attractors. This may also be reflected in the physical structure of the brain which may also be fractal. EEG data is a good place to look for the underlying patterns of chaos in the brain since it samples many millions of neurons simultaneously. Several studies have arrived at a fractal dimension of between 5 and 8 for human EEG data. This suggests that the brain operates in a higher dimension than the 4 of traditional space-time. These extra dimensions suggest that quantum gravity may play a role in generating consciousness.
(Image courtesy: Kookmin University)
Infants develop the ability to consciously process their environment as early as five months of age, according to a study published in the journal Science.
The team of French and Danish researchers, led by neuroscientist Sid Kouider, discovered a signal in the nervous system of infants that reliably identifies the beginning of visual consciousness, or the ability to see something and recall that you have seen it.
The team set out believing infants had the capacity for conscious reflection, but they had to overcome the barrier that babies could not report their thoughts.
They used electroencephalography (EEG) to record electrical activity in the brains of 80 infants aged five, 12 and 15 months while they were shown pictures of faces and random patterns for a fraction of a second.
When adults are aware of a stimulus, their brains show a two-stage pattern of activity. When they see a moving object, the sensors in the vision centre of the brain activate with a spike of activity.
The signal then moves from the back of the brain to the prefrontal cortex, which deals with higher-level cognition. This is known as the late slow wave.
Conscious awareness begins after the second stage of neural activity reaches a specific threshold.
The new study found this two-stage pattern of brain activity was present in the three groups of infants, though it was weaker and more drawn out in the five-month-olds.
The researchers say neurological markers of visual consciousness may help paediatricians better manage infant pain and anaesthesia.
But they note the research does not provide direct proof of consciousness. “Indeed, it is a genuine philosophical problem whether such a proof can ever be obtained from purely neurophsysiological data,” the paper said.
Professor Louise Newman, Director of the Centre for Developmental Psychiatry & Psychology at Monash University, said the study was novel in its ability to measure the way very young brains register stimuli.
But five months should not be seen as a fixed point at which infants start to process information, she said.
“Although this group has studied five months and up, my suspicion would be that if we had different techniques, young infants – from birth on – would show the capacity of registering these sorts of stimuli.
“Infants are born with quite sophisticated capacities to observe, respond to and interact with the environment, particularly the social environment,” she said.
“Very soon after birth, infants will maintain gaze with their parents or parent: they’ve got quite sophisticated visual tracking capacity from an early age.”
Professor Newman, who has undertaken behavioural studies in two- to four-month olds, said young infant brains were extremely sensitive to their mother’s emotional reaction.
“They learn that ‘if I do this, or if I smile or signal in this way, this is what usually happens’. If you manipulate that so they don’t get that response, they’re very sensitive to that and they show signs that it’s very aversive to them.”
A team of researchers led by Associate Professor Maria Kozhevnikov from the Department of Psychology at the National University of Singapore (NUS) Faculty of Arts and Social Sciences showed, for the first time, that it is possible for core body temperature to be controlled by the brain. The scientists found that core body temperature increases can be achieved using certain meditation techniques (g-tummo) which could help in boosting immunity to fight infectious diseases or immunodeficiency.
Published in science journal PLOS ONE in March 2013, the study documented reliable core body temperature increases for the first time in Tibetan nuns practising g-tummo meditation. Previous studies on g-tummo meditators showed only increases in peripheral body temperature in the fingers and toes. The g-tummo meditative practice controls “inner energy” and is considered by Tibetan practitioners as one of the most sacred spiritual practices in the region. Monasteries maintaining g-tummo traditions are very rare and are mostly located in the remote areas of eastern Tibet.
The researchers collected data during the unique ceremony in Tibet, where nuns were able to raise their core body temperature and dry up wet sheets wrapped around their bodies in the cold Himalayan weather (-25 degree Celsius) while meditating. Using electroencephalography (EEG) recordings and temperature measures, the team observed increases in core body temperature up to 38.3 degree Celsius. A second study was conducted with Western participants who used a breathing technique of the g-tummo meditative practice and they were also able to increase their core body temperature, within limits.
Applications of the research findings
The findings from the study showed that specific aspects of the meditation techniques can be used by non-meditators to regulate their body temperature through breathing and mental imagery. The techniques could potentially allow practitioners to adapt to and function in cold environments, improve resistance to infections, boost cognitive performance by speeding up response time and reduce performance problems associated with decreased body temperature.
The two aspects of g-tummo meditation that lead to temperature increases are “vase breath” and concentrative visualisation. “Vase breath” is a specific breathing technique which causes thermogenesis, which is a process of heat production. The other technique, concentrative visualisation, involves focusing on a mental imagery of flames along the spinal cord in order to prevent heat losses. Both techniques work in conjunction leading to elevated temperatures up to the moderate fever zone.
Assoc Prof Kozhevnikov explained, “Practicing vase breathing alone is a safe technique to regulate core body temperature in a normal range. The participants whom I taught this technique to were able to elevate their body temperature, within limits, and reported feeling more energised and focused. With further research, non-Tibetan meditators could use vase breathing to improve their health and regulate cognitive performance.”
Further research into controlling body temperature
Assoc Prof Kozhevnikov will continue to explore the effects of guided imagery on neurocognitive and physiological aspects. She is currently training a group of people to regulate their body temperature using vase breathing, which has potential applications in the field of medicine. Furthermore, the use of guided mental imagery in conjunction with vase breathing may lead to higher body temperature increases and better health.
Scientists have known for some time that the human brain’s ability to stay calm and focused is limited and can be overwhelmed by the constant noise and hectic, jangling demands of city living, sometimes resulting in a condition informally known as brain fatigue.
With brain fatigue, you are easily distracted, forgetful and mentally flighty — or, in other words, me.
But an innovative new study from Scotland suggests that you can ease brain fatigue simply by strolling through a leafy park.
The idea that visiting green spaces like parks or tree-filled plazas lessens stress and improves concentration is not new. Researchers have long theorized that green spaces are calming, requiring less of our so-called directed mental attention than busy, urban streets do. Instead, natural settings invoke “soft fascination,” a beguiling term for quiet contemplation, during which directed attention is barely called upon and the brain can reset those overstretched resources and reduce mental fatigue.
But this theory, while agreeable, has been difficult to put to the test. Previous studies have found that people who live near trees and parks have lower levels of cortisol, a stress hormone, in their saliva than those who live primarily amid concrete, and that children with attention deficits tend to concentrate and perform better on cognitive tests after walking through parks or arboretums. More directly, scientists have brought volunteers into a lab, attached electrodes to their heads and shown them photographs of natural or urban scenes, and found that the brain wave readouts show that the volunteers are more calm and meditative when they view the natural scenes.
But it had not been possible to study the brains of people while they were actually outside, moving through the city and the parks. Or it wasn’t, until the recent development of a lightweight, portable version of the electroencephalogram, a technology that studies brain wave patterns.
For the new study, published this month in The British Journal of Sports Medicine, researchers at Heriot-Watt University in Edinburgh and the University of Edinburgh attached these new, portable EEGs to the scalps of 12 healthy young adults. The electrodes, hidden unobtrusively beneath an ordinary looking fabric cap, sent brain wave readings wirelessly to a laptop carried in a backpack by each volunteer.
The researchers, who had been studying the cognitive impacts of green spaces for some time, then sent each volunteer out on a short walk of about a mile and half that wound through three different sections of Edinburgh.
The first half mile or so took walkers through an older, historic shopping district, with fine, old buildings and plenty of pedestrians on the sidewalk, but only light vehicle traffic.
The walkers then moved onto a path that led through a park-like setting for another half mile.
Finally, they ended their walk strolling through a busy, commercial district, with heavy automobile traffic and concrete buildings.
The walkers had been told to move at their own speed, not to rush or dawdle. Most finished the walk in about 25 minutes.
Throughout that time, the portable EEGs on their heads continued to feed information about brain wave patterns to the laptops they carried.
Afterward, the researchers compared the read-outs, looking for wave patterns that they felt were related to measures of frustration, directed attention (which they called “engagement”), mental arousal and meditativeness or calm.
What they found confirmed the idea that green spaces lessen brain fatigue.
When the volunteers made their way through the urbanized, busy areas, particularly the heavily trafficked commercial district at the end of their walk, their brain wave patterns consistently showed that they were more aroused, attentive and frustrated than when they walked through the parkland, where brain-wave readings became more meditative.
While traveling through the park, the walkers were mentally quieter.
Which is not to say that they weren’t paying attention, said Jenny Roe, a professor in the School of the Built Environment at Heriot-Watt University, who oversaw the study. “Natural environments still engage” the brain, she said, but the attention demanded “is effortless. It’s called involuntary attention in psychology. It holds our attention while at the same time allowing scope for reflection,” and providing a palliative to the nonstop attentional demands of typical, city streets.
Of course, her study was small, more of a pilot study of the nifty new, portable EEG technology than a definitive examination of the cognitive effects of seeing green.
But even so, she said, the findings were consistent and strong and, from the viewpoint of those of us over-engaged in attention-hogging urban lives, valuable. The study suggests that, right about now, you should consider “taking a break from work,” Dr. Roe said, and “going for a walk in a green space or just sitting, or even viewing green spaces from your office window.” This is not unproductive lollygagging, Dr. Roe helpfully assured us. “It is likely to have a restorative effect and help with attention fatigue and stress recovery.”
-by Gretchen Reynolds, The New York Times
Electroencephalogram (EEG), which measures and records electrical activity in the brain, is a quick and efficient way of determining whether seizures are the cause of altered mental status (AMS) and spells, according to a study by scientists at the UC San Francisco.
The research, which focused on patients who had been given an EEG after being admitted to the hospital for symptoms such as AMS and spells, appears on March 27 in Mayo Clinic Proceedings.
“We have demonstrated a surprisingly high frequency of seizures – more than 7 percent – in a general inpatient population,” said senior investigator John Betjemann, MD, a UCSF assistant professor of neurology. “This tells us that EEG is an underutilized diagnostic tool, and that seizures may be an underappreciated cause of spells and AMS.”
The results are important, he said, because EEG can identify treatable causes of AMS or spells, and because “it can prompt the physician to look for an underlying reason for seizures in persons who did previously have them.”
Seizures are treatable with a number of FDA-approved anticonvulsants, he said, “so patients who are quickly diagnosed can be treated more rapidly and effectively. This may translate to shorter lengths of stay and improved patient outcomes.”
In one of the first studies of its kind, Betjemann and his team analyzed the medical records of 1,048 adults who were admitted to a regular inpatient unit of a tertiary care hospital and who underwent an EEG. They found that 7.4 percent of the patients had a seizure of some kind while being monitored.
“As I tell my patients, seizures come in all different flavors, from a dramatic convulsion to a subtle twitching of the face or hand or finger,” said Betjemann. “There might be no outward manifestation at all, other than that the person seems a little spacey. It’s easily missed by family members and physicians alike, but can be picked up by EEG.”
Another 13.4 percent of patients had epileptiform discharges, which are abnormal patterns that indicate patients are at an increased risk of seizures.
Almost 65 percent of patients had their first seizure within one hour of EEG recording, and 89 percent within six hours.
“This is good news for smaller hospitals that don’t have 24 hour EEG coverage, but that do have a technician on duty during the day,” Betjemann said.
He speculated that lack of 24-hour coverage is a major reason that EEG is not used as an inpatient diagnostic tool as often as it might be. “This paper shows that, fortunately, it’s not necessary. Almost two thirds of patients with seizures can be identified in the first hour, and almost 90 percent in the course of a shift.”
EEGs are easy to obtain, painless and noninvasive, said Betjemann. “The technician applies some paste and electrodes and hooks up the machine. All the patient has to do is rest in bed.”
Betjemann said that the next logical research step would be a prospective study. “We have to start at the beginning, see if patients are altered when they are admitted, and do an EEG in a formal standardized setting. Then we’d want to see how often EEG is changing the management of patients – either starting or stopping medications,” he said. “A patient may be having spells, and an EEG might tell you this is not a seizure, and that it’s important not to treat it with anti-epileptic medications.”
(Image: Rex Features)
In the laboratories of the Henry Wellcome Building at Birkbeck, University of London, children’s squeaky toys lie scattered on the floor. Brightly coloured posters of animals are pasted on the walls and picture books are stacked on the low tables. This is the Babylab — a research centre that experiments on children aged one month to three years, to understand how they learn, develop and think. “The way babies’ brains change is an amazing and mysterious process,” says the lab director, psychologist Mark Johnson. “The brain increases in size by three- to four-fold between birth and teenage years, but we don’t understand how that relates to its function.”
The Birkbeck neuroscientists are interested in finding out how babies recognise faces, how they learn to pay attention to some things and not others, how they perceive emotion and how their language develops. Studies published by the lab have shown that babies prefer to look at faces over objects. They have also found that differences in the dopamine-producing gene can affect babies’ attention span and that at six to eight months of age, there are detectable differences in the brain patterns of babies who were later diagnosed with autism.
The biggest obstacle is designing the right kinds of experiment. “There aren’t many methods for getting inside the mind of an infant or a toddler,” Johnson explains. Graduate students at the Babylab have teamed up with technology companies, using a €1.9 million (£1.7 million) grant from the European Union, to develop tools such as EEG head nets that record electrical brain activity, helmets that use light to measure blood flow in different parts of the brain, and eye-trackers that help study attention. Eventually, they want to create wireless systems so babies can react and play naturally during experiments. But despite the wires, “all our studies are geared towards making sure our babies are contented,” says Johnson. “If we want data, we need happy babies.”
Our understanding of brain activity has traditionally been linked to brain areas – when we speak, the speech area of the brain is active. New research by an international team of psychologists led by David Alexander and Cees van Leeuwen (Laboratory for Perceptual Dynamics) shows that this view may be overly rigid. The entire cortex, not just the area responsible for a certain function, is activated when a given task is initiated. Furthermore, activity occurs in a pattern: waves of activity roll from one side of the brain to the other.
The brain can be studied on various scales, researcher David Alexander explains: “You have the neurons, the circuits between the neurons, the Brodmann areas – brain areas that correspond to a certain function – and the entire cortex. Traditionally, scientists looked at local activity when studying brain activity, for example, activity in the Brodmann areas. To do this, you take EEG’s (electroencephalograms) to measure the brain’s electrical activity while a subject performs a task and then you try to trace that activity back to one or more brain areas.”
In this study, the psychologists explore uncharted territory: “We are examining the activity in the cerebral cortex as a whole. The brain is a non-stop, always-active system. When we perceive something, the information does not end up in a specific part of our brain. Rather, it is added to the brain’s existing activity. If we measure the electrochemical activity of the whole cortex, we find wave-like patterns. This shows that brain activity is not local but rather that activity constantly moves from one part of the brain to another. The local activity in the Brodmann areas only appears when you average over many such waves.”
Each activity wave in the cerebral cortex is unique. “When someone repeats the same action, such as drumming their fingers, the motor centre in the brain is stimulated. But with each individual action, you still get a different wave across the cortex as a whole. Perhaps the person was more engaged in the action the first time than he was the second time, or perhaps he had something else on his mind or had a different intention for the action. The direction of the waves is also meaningful. It is already clear, for example, that activity waves related to orienting move differently in children – more prominently from back to front – than in adults. With further research, we hope to unravel what these different wave trajectories mean.”
A new study conducted by monitoring the brain waves of sleeping adolescents has found that remarkable changes occur in the brain as it prunes away neuronal connections and makes the major transition from childhood to adulthood.
“We’ve provided the first long-term, longitudinal description of developmental changes that take place in the brains of youngsters as they sleep,” said Irwin Feinberg, professor emeritus of psychiatry and behavioral sciences and director of the UC Davis Sleep Laboratory. “Our outcome confirms that the brain goes through a remarkable amount of reorganization during puberty that is necessary for complex thinking.”
The research, published in the February 15 issue of American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, also confirms that electroencephalogram, or EEG, is a powerful tool for tracking brain changes during different phases of life, and that it could potentially be used to help diagnose age-related mental illnesses. It is the final component in a three-part series of studies carried out over 10 years and involving more than 3,500 all-night EEG recordings. The data provide an overall picture of the brain’s electrical behavior during the first two decades of life.
Feinberg explained that scientists have generally assumed that a vast number of synapses are needed early in life to recover from injury and adapt to changing environments. These multiple connections, however, impair the efficient problem solving and logical thinking required later in life. His study is the first to show how this shift can be detected by measuring the brain’s electrical activity in the same children over the course of time.
Two earlier studies by Feinberg and his colleagues showed that EEG fluctuations during the deepest (delta or slow wave) phase of sleep, when the brain is most recuperative, consistently declined for 9- to 18-year-olds. The most rapid decline occurred between the ages of 12 and 16-1/2. This led the team to conclude that the streamlining of brain activity — or “neuronal pruning” — required for adult cognition occurs together with the timing of reproductive maturity.
Questions remained, though, about electrical activity patterns in the brains of younger children.
For the current study, Feinberg and his research team monitored 28 healthy, sleeping children between the ages of 6 and 10 for two nights every six months. The new findings show that synaptic density in the cerebral cortex reaches its peak at age 8 and then begins a slow decline. The recent findings also confirm that the period of greatest and most accelerated decline occurs between the ages of 12 and 16-1/2 years, at which point the drop markedly slows.
“Discovering that such extensive neuronal remodeling occurs within this 4-1/2 year timeframe during late adolescence and the early teen years confirms our view that the sleep EEG indexes a crucial aspect of the timing of brain development,” said Feinberg.
The latest study also confirms that EEG sleep analysis is a powerful approach for evaluating adolescent brain maturation, according to Feinberg. Besides being a relatively simple, accessible technology for measuring the brain’s electrical activity, it is more accurate than more cumbersome and expensive options.
“Structural MRI, for instance, has not been able to identify the adolescent accelerations and decelerations that are easily and reliably captured by sleep EEG,” said Feinberg. “We hope our data can aid the search for the unknown genetic and hormonal biomarkers that drive those fluctuations. Our data also provide a baseline for seeking errors in brain development that signify the onset of diseases such as schizophrenia, which typically first become apparent during adolescence. Once these underlying processes have been identified, it may become possible to influence adolescent brain changes in ways that promote normal development and correct emerging abnormalities.”
The stick can work just as well as the carrot in improving our performance, a team of academics at The University of Nottingham has found.
A study led by researchers from the University’s School of Psychology, published recently in the Journal of Neuroscience, has shown that punishment can act as a performance enhancer in a similar way to monetary reward.
Dr Marios Philiastides, who led the work, said: “This work reveals important new information about how the brain functions that could lead to new methods of diagnosing neural development disorders such as autism, ADHD and personality disorders, where decision-making processes have been shown to be compromised.”
The Nottingham study aimed at looking at how the efficiency with which we make decisions based on ambiguous sensory information — such as visual or auditory — is affected by the potential for, and severity of, anticipated punishment.
To investigate this, they asked participants in the study to perform a simple perceptual task — asking them to judge whether a blurred shape behind a rainy window is a person or something else.
They punished incorrect decisions by imposing monetary penalties. At the same time, they measured the participants’ brain activity in response to different amounts of monetary punishment. Brain activity was recorded, non-invasively, using an EEG machine which detects and amplifies brain signals from the surface of the scalp through a set of small electrodes embedded in a swim-like cap fitted on the participants’ head.
They found that participants’ performance increased systematically as the amount of punishment increased, suggesting that punishment acts as a performance enhancer in a similar way to monetary reward.
At the neural level, the academics identified multiple and distinct brain activations induced by punishment and distributed throughout different areas of the brain. Crucially, the timing of these activations confirmed that the punishment does not influence the way in which the brain processes the sensory evidence but does have an impact on the brain’s decision maker responsible for decoding sensory information at a later stage in the decision-making process.
Finally, they showed that those participants who showed the greatest improvements in performance also showed the biggest changes in brain activity. This is a key finding as it provides a potential route to study differences between individuals and their personality traits in order to characterise why some may respond better to reward and punishment than others.
A more thorough understanding of the influence of punishment on decision-making and how we make choices could lead to useful information on how to use incentive-based motivation to encourage certain behaviour.
The paper, Temporal Characteristics of the Influence of Punishment on Perceptual Decision Making in the Human Brain, is available online via the Journal of Neuroscience.
Every year thousands of people in Europe are paralysed by a spinal cord injury. Many are young adults, facing the rest of their lives confined to a wheelchair. Although no medical cure currently exists, in the future they could be able to walk again thanks to a mind-controlled robotic exoskeleton being developed by EU-funded researchers.
The system, based on innovative ‘Brain-neural-computer interface’ (BNCI) technology - combined with a light-weight exoskeleton attached to users’ legs and a virtual reality environment for training - could also find applications in the rehabilitation of stroke victims and in assisting astronauts rebuild muscle mass after prolonged periods in space.
In the United Kingdom, every eight hours someone suffers a spinal cord injury, often leading to partial or full lower-body paralysis. In the United States, more than 250.000 people are living with paralysis as a result of damage to their spinal cord, usually because of a traffic accident, fall or sporting injury. Many are under the age of 50, and with no known medical cure or way of repairing damaged spinal nerves they face the rest of their lives in a wheelchair.
But by bypassing the spinal cord entirely and routing brain signals to a robotic exoskeleton, they should be able to get back on their feet. That is the ultimate goal of researchers working in the ‘Mind-controlled orthosis and VR-training environment for walk empowering’ (Mindwalker) project, a three-year initiative supported by EUR 2.75 million in funding from the European Commission.
‘Mindwalker was proposed as a very ambitious project intended to investigate promising approaches to exploit brain signals for the purpose of controlling advanced orthosis, and to design and implement a prototype system demonstrating the potential of related technologies,’ explains Michel Ilzkovitz, the project coordinator at Space Applications Services in Belgium.
The team’s approach relies on an advanced BNCI system that converts electroencephalography (EEG) signals from the brain, or electromyography (EMG) signals from shoulder muscles, into electronic commands to control the exoskeleton.
The Laboratory of Neurophysiology and Movement Biomechanics at the Université Libre de Bruxelles (ULB) focused on the exploitation of EEG and EMG signals treated by an artificial neural network, while the Foundation Santa Lucia in Italy developed techniques based on EMG signals modelled by the coupling of neural and biomechanical oscillators.
One approach for controlling the exoskeleton uses so-called ‘steady-state visually evoked potential’, a method that reads flickering visual stimuli produced at different frequencies to induce correlated EEG signals. Detection of these EEG signals is used to trigger commands such as ‘stand’, ‘walk’, ‘faster’ or ‘slower’.
A second approach is based on processing EMG signals generated by the user’s shoulders and exploits the natural arm-leg coordination in human walking: arm-swing patterns can be perceived in this way and converted into control signals commanding the exoskeleton’s legs.
A third approach, ‘ideation’, is also based on EEG-signal processing. It uses the identification and exploitation of EEG Theta cortical signals produced by the natural mental process associated with walking. The approach was investigated by the Mindwalker team but had to be dropped due to the difficulty, and time needed, in turning the results of early experiments into a fully exploitable system.
Regardless of which method is used, the BNCI signals have to be filtered and processed before they can be used to control the exoskeleton. To achieve this, the Mindwalker researchers fed the signals into a ‘Dynamic recurrent neural network’ (DRNN), a processing technique capable of learning and exploiting the dynamic character of the BNCI signals.
‘This is appealing for kinematic control and allows a much more natural and fluid way of controlling an exoskeleton,’ Mr Ilzkovitz says.
The team adopted a similarly practical approach for collecting EEG signals from the user’s scalp. Most BNCI systems are either invasive, requiring electrodes to be placed directly into brain tissue, or require users to wear a ‘wet’ capon their head, necessitating lengthy fitting procedures and the use of special gels to reduce the electrical resistance at the interface between the skin and the electrodes. While such systems deliver signals of very good quality and signal-to-noise ratio, they are impractical for everyday use.
The Mindwalker team therefore turned to a ‘dry’ technology developed by Berlin-based eemagine Medical Imaging Solutions: a cap covered in electrodes that the user can fit themselves, and which uses innovative electronic components to amplify and optimise signals before sending them to the neural network.
‘The dry EEG cap can be placed by the subject on their head by themselves in less than a minute, just like a swimming cap,’ Mr Ilzkovitz says.